JPS6131049B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing graphite fluoride represented by the formula (C ₂ F) _o . More particularly, the present invention relates to an improved method for producing (C ₂ F) _o using expanded graphite as the carbon material. Conventionally, graphite fluoride (CF ₎ has been known to have the structure synthesized from carbon and fluorine, and due to its unique properties, graphite fluoride (CF ₎ has been used as an active material in batteries and as a lubricant. agent, wetting agent, antifouling agent,
It is highly valued industrially in a wide range of fields, including as a water and oil repellent. Furthermore, recently, (C ₂ F) _o- type fluorinated graphite, which has a novel structure and can be produced at relatively low cost and with high yield, has become an industrially viable graphite similar to (CF) _o due to its unique chemical and physical properties. It is attracting attention as a material. The reaction for producing these two types of fluorinated graphite is expressed by the following equation. 2nC(s)+nF ₂ (g) → 2(CF) _o (s) …(1) 4nC(s)+nF ₂ (g)→ 2(C ₂ F) _o (s) …(2) In the above reaction As the fluorine, fluorine alone or fluorine gas diluted with an inert gas is used, but there are many types of carbon represented by C, and the structure is complex, so the reaction conditions are diverse. The fact that the composition and crystallinity of the products also vary somewhat is similar to the way that the properties of carbon and graphite vary along with their structures. Furthermore, these graphite fluorides have various technical and economical drawbacks during their manufacturing process, one of which is (CF) in the case of _o- type graphite fluoride, whose degree of thermal decomposition is within the production temperature range of graphite fluoride. The point is that it is close to . For example, when natural graphite is used as a carbon material, it requires a high temperature of 500°C or more and a long reaction time. For example, if the fluorination reaction is carried out at around 600°C for 24 hours ₍ CF) However, since the (CF) _o obtained in this way decomposes at 610℃, the difference between the generation temperature and the thermal decomposition temperature is about 10 to 50℃.
It is very close to ℃. In addition, both the production and decomposition reactions of fluorinated graphite are exothermic reactions, so once the temperature rises during the production reaction stage and the produced fluorinated graphite exceeds a certain temperature, thermal decomposition occurs, and furthermore, this Thermal decomposition also presents the difficult problem of increasing the temperature of the reaction system. This accelerates the decomposition of graphite fluoride, and sometimes the temperature of the entire reaction system rises to a temperature higher than the decomposition temperature of graphite fluoride. It decomposes into. Due to this fact, conventional (CF) _o
The yield of fluorinated graphite expressed by Methods have been adopted in which the process is carried out in several stages, but the former is difficult to control the temperature of, and the latter has a complicated manufacturing process, so it is not industrially practical. On the other hand, (C ₂ F) _o -type fluorinated graphite has almost the same properties and uses as (CF) _o , but the amount of expensive fluorine can be significantly reduced in its production, and the new New uses are being developed due to its characteristics, and the manufacturing method is described in detail by the present inventors in Japanese Patent Application Laid-Open No. 102893/1983.
It can be produced by fluorination at 300-500°C. However, in order to obtain (C ₂ F) _o with high selectivity, it is preferable that the Franklin P-value of the carbon material to be subjected to the reaction is close to 0; If
The time required for the raw graphite to be completely fluorinated to produce (C ₂ F) _o is extremely long, especially under mild reaction conditions favorable for selectively obtaining (C ₂ F) _o , e.g. 200~250mesh (Tyler) natural graphite from Madagascar at 375℃, fluorine pressure 200mmHg
When reacted with fluorine, it takes as long as 120 hours for its formation. Here, the Franklin P-value indicates the degree of crystallinity of graphite, that is, the degree of graphitization, and can be obtained by calculating from the following formula. d ₍₀₀₂₎ = 3.440−0.086 (1−P ² ) (wherein, d ₍₀₀₂₎ is the interplanar spacing (dd ₀₀₂ ) measured by X-ray diffraction, and P indicates the Franklin P value) [R ．． E. REFranklin, Acta Cryst.
Volume 4, p. 235 (1951)]. Therefore, in an attempt to shorten the generation time,
For example, (1) using graphite with a small particle size, (2) increasing the reaction temperature, and (3) increasing the fluorine pressure have been used, but each method (1) tends to cause decomposition reactions. (2) the purity of the produced (C ₂ F) _o decreases, and (3) the corresponding effect is small. Therefore, the inventors of the present invention have conducted various researches to develop a production method that efficiently produces (C ₂ F) _o with high selectivity in a short period of time. The present invention was completed after discovering that the intended purpose could be achieved. Therefore, one object of the present invention is to provide an improved production method for efficiently producing graphite fluoride represented by (C ₂ F) _o in a shortened reaction time. Another object of the present invention is to further improve the above-mentioned production method from the viewpoint of chemical engineering, and to provide a method for carrying out the production on an excellent reactor scale. These and other objects, features and advantages will become apparent from the following description. Basically, according to the present invention, fluorinated graphite expressed by the formula (C ₂ F) _o is produced by reacting a carbon material and fluorine under a fluorine pressure of 100 to 760 mmHg at a temperature of 300 to 500 °C. There is provided a method for producing graphite fluoride, characterized in that the method uses, as a carbon material, expanded graphite obtained by expanding a graphite raw material with a Franklin P-value of 0 to 0.4 until its bulk specific gravity becomes less than 0.01. Ru. Graphite, which is the raw material for the expanded graphite used in the method for producing (C ₂ F) _o according to the present invention _, is a Franklin _P.
- The value must be in the range 0 to 0.4.
Expanded graphite is made by rapidly heating a graphite intercalation compound such as natural graphite, artificial graphite, or hardwood graphite to instantaneously decompose the interlayer compound layer and gasify it, and the resulting pressure expands the distance between the graphite layers. Generally, the manufacturing method involves using graphite powder with high anisotropy in a mixture of various oxidizing agents and oxidizing mixtures (e.g. nitric acid, potassium chlorate, chromic acid, potassium permanganate,
Graphite by treatment with potassium chromate, potassium dichromate, perchloric acid, or concentrated solutions of e.g. nitric acid and potassium chlorate, chromic acid and phosphoric acid, sulfuric acid and nitric acid, and also e.g. mixtures of sulfuric acid and hydrogen peroxide. A method of generating an intercalation compound, washing it thoroughly with water, drying it, and then rapidly heating it at a high temperature of approximately 500 to 1000℃, or electrolysis containing a substance (such as sulfuric acid) that reacts with graphite to create a graphite intercalation compound. After electrolytic oxidation treatment in a liquid using graphite as an anode to generate a graphite intercalation compound, electrolytic reduction is performed using this as a cathode to decompose the graphite intercalation compound, and then rapid oxidation at approximately 500 to 1000℃ for expansion. There are various methods such as heat treatment. The bulk specific gravity of the expanded graphite obtained by this expansion treatment depends on the type of interlayer intercalating substance,
Although it varies depending on the heating temperature and time, in the method of the present invention, the bulk specific gravity is less than 0.01, preferably 0.003.
By expanding to ~0.007, (C ₂ F) _o
A significant reduction in reaction time is achieved without compromising the selectivity to . According to another aspect of the present invention, fluorinated graphite expressed by the formula (C ₂ F) _o is produced by reacting a carbon material and fluorine under a fluorine pressure of 100 to 760 mmHg at a temperature of 300 to 500°C. In the manufacturing method, the carbon material is expanded graphite obtained by expanding graphite raw material with a Franklin P value of 0 to 0.4 until the bulk specific gravity becomes less than 0.01, and the specific gravity is increased until the bulk specific gravity is in the range of 0.01 to 0.2. Provided is a method for producing graphite fluoride, which comprises using a method of producing graphite fluoride. Generally, if natural graphite is immersed in a mixed solution of concentrated sulfuric acid (95-98%) and hydrogen peroxide to generate a graphite intercalation compound, washed with water, dried, and then heat-treated at 800°C for several tens of seconds, the bulk specific gravity is approximately 0.004. of expanded graphite is obtained. This is a carbon raw material that can accomplish the purpose of the present invention as it is, but by wet-pulverizing it by adding water at a volume ratio of 1:1, the bulk specific gravity increases, which is surprising. Even if a carbon material that has been expanded and has a bulk specific gravity in the range of 0.01 to 0.2 is used as a carbon raw material for fluorination, the effect is almost not as great as when using one with a bulk specific gravity of 0.004. It was found that the reaction time was shortened while maintaining the excellent selectivity to (C ₂ F) _o . This is extremely advantageous in practice in that it prevents the reactor from increasing in size. As a method for increasing the bulk specific gravity, any suitable method such as the above-mentioned wet grinding or compression using a screw type homomixer can be used, but
The above wet method is preferably used. Preferred liquids for use therein include water, alcohols that are easily soluble in water such as methyl alcohol, ethyl alcohol, and isopropyl alcohol, and their aqueous solutions, diols that are easily soluble in water such as ethylene glycol, propylene glycol, and butylene glycol; Carbon tetrachloride, especially water, is easy to handle and is preferred from the economic point of view. It is not clear why carbon materials using expanded graphite have a faster reaction rate than those using normal graphite materials, even at low temperatures, but expanded graphite has a larger crystallite size in the C-axis direction. This makes it easier to supply fluorine molecules from the bottom of graphite fluoride to the reaction interface, and when residuals such as oxidized substances in graphite are released into the atmosphere by heating, new molecules are created inside graphite. It is thought that lattice defects and grain boundaries are created, and these active sites serve as starting points for new fluorination reactions, promoting the reaction. Fluorinated graphite (C ₂ F ₎ obtained by fluorination reaction usually exhibits a black or gray-black color, but it is exposed to a fluorine atmosphere at a temperature ranging from about 50°C higher than the formation temperature to about 600°C. If heat treatment (crystallization) is performed inside, the chemical composition (fluorine content) will not change, that is, it will remain stable without changing to (CF) _o , and only the color will become white and the crystallinity will increase. . If (C ₂ F) _o is produced by the fluorination reaction using expanded graphite as a carbon material in this way, the reaction rate can be improved by at least twice as much as that using ordinary graphite. (C ₂ F) _o
Even when crystallizing fluorinated graphite (C 2 F), there is an advantage that graphite _fluoride (C ₂ F) with high crystallinity, that is, with improved whiteness, can be easily obtained. According to the method of the present invention using such expanded graphite, it is possible to easily and efficiently produce graphite fluoride represented by (C ₂ F) _o even at low temperatures in a short time and with high selectivity. The industrial value is extremely large. The present invention will be explained in more detail with reference to Examples below, but the scope of the present invention is not limited to the Examples. Example 1 and Comparative Examples 1 to 2 48 to 80 mesh (Tyler) 98 to 100 parts by weight of natural graphite from Madagascar (Franklin P-value = 0)
% sulfuric acid (300 parts by weight) and hydrogen peroxide (10 parts by weight)
An intercalation compound was produced by adding a mixed solution of the mixture, washed with water, dried, and then heat-treated at 800°C for 20 seconds to obtain expanded graphite with a bulk specific gravity of 0.004. A fluorine-resistant thermobalance was used as the reaction apparatus. 30 mg of the expanded graphite was collected in a thermobalance, and first heated at 500° C. under vacuum (degree of vacuum of 10 ^-2 mmHg or more) for about 30 minutes to remove moisture. Next, fluorine was introduced into the thermobalance from the fluorine cylinder and reacted at a reaction temperature of 380°C while maintaining the fluorine pressure at 760 mmHg. The time required for complete fluorination to produce (C ₂ F) _o was as short as 5 hours, and the yield was 100% based on graphite. In the X-ray diffraction diagram of fluorinated graphite obtained from expanded graphite, 2θ = 9.8.
There was a diffraction line with a peak at °, confirming that (C ₂ F) _o- type graphite fluoride was produced. The composition of the product was _{CF 0.66} . For comparison, 48 to 80 mesh natural graphite before expansion (Comparative Sample 1) and fine natural graphite of 400 mesh or more (Comparative Sample 2) were each fluorinated under the same conditions as above. The time required for complete fluorination to produce (C ₂ F) _o was over 200 hours for Comparative Sample 1 and 3 hours for Comparative Sample 2. Example 2 In the production of (C ₂ F) _o by complete fluorination of expanded graphite obtained in the same manner as in Example 1, the reaction conditions were the same as in Example 1 except for the reaction temperature. Table 1 shows the production time, composition and yield of the produced graphite fluoride. For convenience, the data of Example 1 is also shown.

[Table] Example 3 Water was added to the expanded graphite with a bulk specific gravity of 0.004 used in Example 1 at a volume ratio of 1:1, and the mixture was wet-pulverized using a screw-type homomixer to produce expanded graphite. After increasing the bulk specific gravity to 0.04, 150
(C ₂ F) _o was obtained at each temperature in the same manner as in Example 2, except that the product dried at °C was used for fluorination. The results were substantially the same as those shown in Table 1. Example 4 Similarly to Example 1, using expanded graphite, 380
℃, fluoride pressure of 760 mmHg for 5 hours, the reaction temperature was raised at a heating rate of 5° C./min, and crystallized under the predetermined conditions shown in Table 2. The whiteness of the product was measured using a reflectance meter (Nippon Denshoku CP6-1D).
A comparison was made based on the reflectance measured. In addition, the thermal decomposition onset temperature in an air atmosphere is DTA (Shimadzu, DT-
20B) at a heating rate of 10°C/min in an air atmosphere. Table 2 shows 380 natural graphite with an average particle size of 10μ.
℃, Fluorine pressure: 760 mmHg, and the results of the reflectance and decomposition onset temperature of fluorinated graphite produced for 30 hours are also shown. Table 2 shows that when fluorinated graphite produced by fluorinating expanded graphite is subsequently crystallized at high temperature in a fluorine atmosphere, it easily becomes more thermally stable and has lower whiteness than when natural graphite is used as a raw material. We were able to obtain high-quality graphite fluoride.

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Claims (1)

[Claims] 1. A method for producing fluorinated graphite represented by the formula (C ₂ F) _o by reacting a carbon material and fluorine under a fluorine pressure of 100 to 760 mmHg at a temperature of 300 to 500°C. . A method for producing fluorinated graphite, characterized in that expanded graphite obtained by expanding a graphite raw material having a Franklin P-value of 0 to 0.4 until its bulk specific gravity becomes less than 0.01 is used as the carbon material. 2 In a method for producing graphite fluoride represented by the formula (C ₂ F) _o by reacting a carbon material and fluorine under a fluorine pressure of 100 to 760 mmHg at a temperature of 300 to 500°C, Franklin Expanded graphite, which is obtained by expanding graphite raw material with a P-value of 0 to 0.4 until the bulk specific gravity becomes less than 0.01, has a bulk specific gravity of 0.01 to 0.01.
A method for producing graphite fluoride, characterized by using graphite whose specific gravity has been increased to a range of 0.2. 3 The expanded graphite contains a graphite intercalation compound of about 500 to about
3. A method according to claim 1 or 2, characterized in that it is obtained by rapid heating at a temperature of 1000°C.